Patients suffering from brain damage such as a stroke, and elderly people have depressed swallowing functions, and often suffer from dysphagia which is a malfunction that food erroneously flows into the trachea or the lung at the time of taking the food. As one method for nutritional supplementation for such people suffering from dysphagia, a tube feeding method for directly administering a liquid diet into the stomach by means of a tube is known. In a patient undergoing the tube feeding, diarrhea is the symptom that is most frequently observed. In a patient undergoing the tube feeding, sufficient attention should be given for the composition of the enteral nutrient, the temperature of the administered nutrient, and the administration speed so as to prevent diarrhea (see Non-Patent Document 1).
It has been conventionally reported that among dietary fibers to be mixed in an enteral nutrient, pectin has a diarrhea-preventing effect (see Non-Patent Document 2). However, it has been also revealed that clear diarrhea-preventing effect is not necessarily exerted only by selecting pectin as the dietary fiber to be mixed in the enteral nutrient (see Non-Patent Document 3).
It has been also reported that low methoxyl pectin having a degree of esterification of 5 to 15% and a viscosity-average molecular weight of 10000 to 35000 can be used as an active ingredient of a diarrhea-preventing agent in enterally administering a nutrient directly to the small intestine without passing through the stomach (see Patent Document 1). However, it is the current state of the art that sufficient diarrhea-preventing effect has not yet been achieved even with the pectin having a structure disclosed in Patent Document 1. Further, since the diarrhea-preventing agent of Patent Document 1 is administered separately from a nutrient, a great burden is imposed on a carer, and if administration is missed, the diarrhea-preventing effect is not obtained, and also there is a drawback that versatility is poor because administration thereof is limited to direct administration to the small intestine.
Meanwhile, pectin is polysaccharide mainly extracted from a pericarp of citrus such as lemon, and is known to have a structure of a linear polysaccharide having a main structure of D-galacturonic acids linked by α-1,4-bonds. Pectin in a cell wall of a plant exists in the state that carboxyl groups of D-galacturonic acids are methyl-esterified with high frequency. The nature of pectin varies depending on the degree of esterification (the ratio of methyl-esterified galacturonic acids: DE value), and pectin is classified into high methoxyl pectin having a degree of esterification of 50% or more and low methoxyl pectin having a degree of esterification of less than 50%. Also, a carboxyl group can be amidated depending on the purification and de-esterification step of pectin. It is known that the degree of esterification and the degree of amidation of pectin (DA value) influence on the gelation characteristics of pectin. However, the mechanism of preventing diarrhea by pectin has not been well elucidated, and whether the difference in structure of pectin leads difference in the diarrhea preventing effect has not been clarified yet.
In addition, nutrients need to stably keep the physical properties during storage, and in particular, enteral nutrients are required to have appropriate viscosity at the time of administration from the view point of easiness of administration, and it is particularly important to stably keep appropriate viscosity during storage. However, for pectins to be conventionally mixed in the nutrient, the relation between the structure of the pectin and the viscosity stability during storage has not been examined so far.